The process consists of a 20-30 minute call with the internal recruiter to discuss the company, the role, your background etc. The next stage is one hour telephone interview based on your knowledge of Gartner, the role and competency questions around Gartner's 4 traits (which they will explain ahead of the interview). The third stage is a WebEx interview with 2 hiring managers which follows a similar format to the previous interview. The final stage is a panel interview in the office, consisting of a pre-prepared presentation, a web demo and some more competency questions.
The whole process was designed to guide you, not to trick you or catch you out. Everyone that I dealt with was really helpful and friendly.